Director of National Intelligence James Clapper called the disclosure of an Internet surveillance program "reprehensible" and said it risks Americans' security.

He said a leak that revealed a program to collect phone records would affect how America's enemies behave and make it harder to understand their intentions.

The top U.S. intelligence official denounced the disclosure of highly secret documents Thursday and sought to set the record straight about how the government collects intelligence about people's telephone and Internet use.

He said he was declassifying some aspects of the monitoring to help Americans understand it better.